Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h, w = map(int, input().split())

#塗れる最大数
#すなわち、（すべての白）ー（最短経路距離）
g = [input() for _ in range(h)]
from collections import *
d = [[-1]*w for _ in range(h)]
d[0][0] = 0

q = deque([(0, 0)])

while q:
    tx, ty = q.popleft()
    for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
        nx, ny = tx + dx, ty + dy
        if 0 <= nx < h and 0 <= ny < w and g[nx][ny] == '.' and d[nx][ny] < 0:
            d[nx][ny] = d[tx][ty] + 1
            q.append((nx, ny))

if d[-1][-1] < 0:
    print(-1)
    exit()
else:
    print(sum([s.count('.') for s in g]) - d[-1][-1] - 1)